Pull-through straightener

ABSTRACT

A STRAIGHTENER FOR METAL STRIP STOCK FROM A STOCK SUPPLY REEL SO THAT THE STRAIGHTENED STOCK MAY BE HANDLED BY AN AUTOMATIC FEED TO A PUNCH PRESS HAS CONVENTIONAL TOP AND BOTTOM GENERALLY HORIZONTAL ARRAYS OF STRAIGHTENER ROLLS. THE GENERALLY HORIZONTAL SPACING BETWEEN LATERALLY OFFSET ADJACENT ROLL AXES IS UNUSUALLY GREAT IN COMPARISION TO CURRENT PRACTICE-IN THE ORDER OF TWO ROLL DIAMETERS. SUCH A ROLL SPACING GREATLY REDUCES POWER REQUIREMENTS FOR PULLING STOCK THROUGH A STRAIGHTENER, HAS OTHER ADVANTAGES SET FORTH IN DETAIL INCLUDING THE ABILITY TO PIVOTALLY SECURE THE TOP ROLL ARRAY, PERMITTING THE STRAIGHTENER TO BE READILY OPENED WITH SUCH A CONSTRUCTION. THE SPACING BETWEEN ADJACENT ROLLS TOWARD THE EXIT END IS PREFERABLY REDUCED FOR OBTAINING DESIRED OPERATING CHARACTERISTICS AS WELL AS FOR GEOMETRICAL REASONS WHERE THE TOP ROLL ARRAY IS PIVOTALLY MOUNTED.

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PULL-THROUGH STRAIGHTENER 3 Sheets-Shoot 2 Sept. 20, 1971 R. G. BODTKE PULL-THROUGH STRAIGHTENER Filed March 30, 1970 United States Patent 3,605,471 PULL-THROUGH STRAIGHTENER Robert Gray Bodtke, 1308 E. Seiberling, Peoria, Ill. 61614 Filed Mar. 30, 1970, Ser. No. 23,862 Int. Cl. B21d N02 US. Cl. 72-165 9 Claims ABSTRACT OF THE DISCLOSURE A straightener for metal strip stock from a stock supply reel so that the straightened stock may be handled by an automatic feed to a punch press has conventional top and bottom generally horizontal arrays of straightener rolls. The generally horizontal spacing between laterally offset adjacent roll axes is unusually great in comparison to current practicein the order of two roll diameters. Such a roll spacing greatly reduces power requirements for pulling stock through a straightener, has other advantages set forth in detail including the ability to pivotally secure the top roll array, permitting the straightener to be readily opened with such a construction. The spacing between adjacent rolls toward the exit end is preferably reduced for obtaining desired operating characteristics as well as for geometrical reasons where the top roll array is pivotally mounted.

This invention relates to a pull-through straightener for metal strip stock. A straightener for metal strip stock is essential when such stock is fed from a reel for final use in a punch press where male and female dies cooperate to produce desired punchings. As a rule, the female die of a die set is below the male die, which generally cooperates with a vertically movable ram.

Metal strip stock from a reel has some curvature along the stock length. Unless straightened, a length of stock will be arcuate when positioned between the die parts preparatory to punching. Cooperating die parts (which are generally made to small tolerances) are designed for flat rather than arcuate stock. Trouble will usually result if punching unstraightened metal stock. Depending upon the mechanical details of stock retention in a press preparatory to stamping, die breakage is an ever present hazard. In addition, spoiled punchings occur frequently.

To overcome the above difliculties, stock straighteners are Widely used. These straighteners utilize a bottom array or series of similar rolls, whose axes are laterally offset in a generally horizontal plane and a top series of similar rolls. The top rolls have their axes laterally offset with respect to each other as well as with respect to the bottom rolls. The pattern of roll surfaces on opposite sides of stock to be worked on is arranged so that stock will first be curved opposite to its original curvature and then reversely curved with decreasing amplitude until stock is sufficiently straightened to be satisfactory.

Such straighteners are designed to handle stock of various widths, usually up to about 30 or 40 inches, and various thicknesses up to the order of about .090 inch. As a rule, stock having a thickness less than about .010 (ten thousandths of an inch) is regarded as thin material requiring one straightener, and the range from about .010 to about .090" (ninety thousandths of an inch) is regarded as heavier stock requiring a different straightener.

Conventional straighteners generally use similar rolls and for the most part have two top and three bottom rolls. However, straighteners are available with seven or more rolls. The total number of rolls is an odd number, there being at least two top rolls and at least three bottom rolls. Many straighteners may have an input stock guide and exit stock guide in the form of rolls or round rods, which have no stock straightening function.

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A common characteristic of such conventional straighteners is the close spacing between adjacent straightener surfaces. The closeness of roll spacing is with reference to roll diameter and involves the radius of curvature to which stock is shaped in progressing along rolls through a straightener. Such a straightener inherently imposes large power requirements on means for moving stock through. The closeness of roll spacing results in relatively short lever arms for bending of stock through successive rolls. Apart from increased pull-through power requirements, the loads on rolls, bearings and the like make it necessary to have heavy duty roll and bearing structures.

Conventional straighteners require individual adjustments for top roll elevation to accommodate different stock thicknesses. Such adjustable supports must be able to withstand heavy roll loading and contribute to the mass and weight of such straighteners. This in turn militates against mechanical designs for opening a straightener to introduce stock, clean rolls, adjust spacing between top and bottom rolls, roll construction and roll finish.

The present invention makes possible a straightener construction which, compared to current structures, is light and flexible and yet able to handle stock with far less power. In addition, the new straightener can handle stock over a wide range of thicknesses without requiring individual top roll adjustments or different straighteners. Instead the new straightener can function with a simple adjustment of the entire top roll array permitting simple bearing supports for each top roll. This makes it possible to mount the top rolls in a frame which may be movable about a pivot axis so that the top rolls can be swung away from the bottom rolls. Such a pivoted construction, because of geometrical as well as tolerance considerations, may require some reduction in spacing between adjacent rolls as the exit end is approached and may also require that some rolls have their axes at somewhat different levels. The fulcrum location as well as stock thickness range are factors in such spacing.

The invention will best be understood in connection with drawings wherein the geometrical as well as structural features will be set forth. For explainatory purposes, certain showings will be exaggerated. Referring now to the drawings;

FIG. 1 is a diagrammatic showing of a five roll arrangement, showing roll spacing of conventional straighteners, this figure being provided for explaining conventional practice.

FIG. 2 is a diagram showing the arrangement of the first three rolls in conventional fashion, except that the two bottom rolls are shown in tangent relation for illustrative purposes; this same figure showing three smaller rolls superimposed upon the larger rolls, the smaller rolls illustrating the new roll arrangement.

FIG. 3 shows a diagram of the roll arrangement of a five roll straightener wherein the first three rolls are spaced in accordance with the present invention and the last three rolls are spaced in accordance with conventional practice.

FIG. 4 is a diagram of a straightener having five rolls arranged to embody the new spacing invention, the top rolls being carried on a top frame which is pivoted for opening the straightener.

FIG. 5 is a polar diagram showing how the five roll axes of FIG. 4 are located.

FIGS. 6, 7 and 8 are respectively side, front and top views of a straightener embodying the present invention, the top being straight up in FIG. 8.

Referring to FIG. 1, a simplified side elevation of a roll arrangement of a conventiontal straightener is illustrated, the axial spacing between adjacent top rolls and between adjacent bottom rolls being no greater than shown and usually being less, the axial spacing considered herein being with relation to roll diameter (or raduis). Various roll diameters are used in the trade and may range from about 1%", or more generally 1 /2 inches, to about 3 inches (or sometimes somewhat more). A five roll straightener is most common, although additional rolls similarly spaced may be provided. The roll pattern illustrated in FIG. 1 has bottom rolls RBI; RB2 and RB3 whose axes are parallel, laterally offset and lie in a substantially horizontal plane. Top rolls RT1 and RT2 have their axes similarly disposed. The rolls have equal diameters and each top roll has its axis above the line of centers of the two adjacent rolls immediately below and intersects such line of centers midway between such adjacent rolls.

It is conventional practice to space adjacent roll axes a bit more than a roll diameter, no more than about 1.25 times a roll diameter. Thus the free space between horizontally spaced roll surfaces would be substantially less than a roll radius and usually of the order of about onehalf a roll radius. The maximum vertical spacing between the top roll line of centers and bottom roll line of centers must be great enough to accomodate the range of stock thickness to be handled. Each top roll has its bearings mounted in vertically adjustable pillow blocks. Such current straightener construction has always been premised on the requirement that heavier stock required larger roll diameter, this usually being about 3 inches. In distinction to this, the new straightener can utilize the same roll diameter, such as about 1 /2", for the entire range of stock thicknesses to be worked on.

As a rule, each top roll is so supported that its bottom arouate portion may be adjusted to lie above to somewhat below the horizontal tangent plane for the tops of the bottom rolls. When top rolls are adjusted for straightening, the top roll axes are not necessarily in one horizontal plane.

The stock is fed to the straightener intake so that the stock curvature is up. Thus the initial bending of stock by the first top roll cooperating with the first two bottom rolls is downward. As a rule, additional stock bending beyond this part of the straightener is less.

FIG. 2 shows one top and two bottom rolls of a conventional roll arrangement the two bottom rolls are shown in tangential arrangement whereas in practice a small clearance between them would be provided) with small diameter rolls superimposed to illustrate the invention, RBI; RB2 and RT1 may be 3" rolls. The stock is shown as curved upwardly by the 3 rolls.

Smaller (half size) rolls R'Bl; R'B2 and RTl are shown with their respective axes vertically displaced. Thus R'Bl has its axis up by one radius as the tops of RBI and R'Bl are tangent. The same is true of R'B2 The axis of RTl is correspondingly displaced downward- 1y so both top rolls are tangent at their bottom portions. The large top roll RT1 is down so that its bottom portion is below the horizontal tangent plane for rolls RBI and RB2 to provide downward stock curvature. Except for lack of clearance between the opposed cylindrical surfaces of RBI and RB2 (these rolls turn in the same direction and require clearance between them) this roll arrangement is conventional.

Now consider the R rolls. The stock does not engage such a large angular part of each roll during straightening. It is clear that stock from the top of R'Bl is free to extend to the bottom of RTl and can do so over a longer lever arm for stock curving. The same is true for RTl to R'BZ. It is clear from FIG. 2, that vertical adjustment of large top roll RT1 will result in a large change of stock contact area in the three rolls. The came vertical adjustment of R'T1 with reference to the lower small rolls will result in a much lower change of contact area with the three small rolls. It follows therefore th a straightener having at least one top roll and two bottom rolls at the intake end spaced as suggested by the small rolls will have more uniform operating characteristics with changes in stock thickness as compared to a conventional straightener using rolls with small spacing between them.

I have found that reducing the relative size of the small rolls compared to the size of the large rolls (here shown as about 1 to 2) does not provide any added substantial advantage. Accordingly, the range of about two times a roll diameter for spacing between laterally offset adjacent rolls in top and bottom rolls is preferred, at least for the first three rolls as shown in FIG. 2.

Referring now to FIG. 3, a straightener is illustrated wherein the first three rolls (one top and two bottom rolls) embodying the invention is joined with two additional rolls cooperating in conventional fashion, in regard to spacing. Thus the added bottom roll is spaced close to the second bottom roll. The added top roll is symmetrically positioned with regard to the two bottom closely spaced rolls. The vertical spacing of the added top roll is conventitonal, with the added roll being vertically adjustable or not. This adjustability is not essential since stock reaching the added top roll has already been straightened to a substantial degree and can be positioned to handle thicker stock.

In fact as rolls are added, the first three (or five) rolls may be spaced to utilize the invention with subsequent rolls added having conventional spacing. The lighter construction for straighteners having at least the first three rolls spaced in accordance with the present invention, makes it possible to have all top rolls mounted in frame which can be clamped to a frame holding the bottom rolls. The construction may be light enough so that the top roll frame may be unclamped and raised to permit introduction of stock into a straightener, clean rolls, etc.

However, it is preferred to have construction where a frame carrying the top rolls is pivotally carried on a frame supporting the bottom rolls. The invention makes such a construction feasible. FIG. 4 shows such a straightener in diagrammatic form.

Bottom frame BF has bottom rolls RBI; RB2 and RB3 carried in bearings. The bottom rolls may have any desired diameter and length. Thus the rolls may have a diameter of about 1 /2" as an example and are long enough to take care of required stock width. The bottom rolls have their axes in a horizontal plane, laterally offset from each other. In accordance with the invention, the axes of rolls RBI (at the intake end of the straightener) and RB2 are offset twice the diameter of a roller, in this particular example, the separation is substantially 3 inches. Top frame TF carries top rolls RT1 and RTZ, similar in size and mounting as the bottom rolls. Top roll RT1 has its axis parallel to the bottom roll axes, vertically offset therefrom and preferably generally symmetrical to bottom rolls RBI and RB2. Top frame TF is pivotally mounted on bottom frame BF to be swingable about axis PA. The location of pivot axis PA is not critical and is most conveniently located below the line of centers for the bottom rolls and at or near the exit end of the straightener. An adjustable pin stop PS may be provided for limiting the closing travel of the top frame to take care of desired stock thickness. Top frame TF will be tightly clamped down during straightening. Top roll RT1 will have its axis spaced about a diameter, or somewhat greater than a diameter, above the line of centers of the bottom rolls. No top rolls require vertical adjustment.

Bottom roll RES is laterally offset from roll RB2 by a somewhat smaller distance than two diameters between the first two rolls RBl and RB2. The reduction in offset is due to geometrical consideration, incident to the pivotal mounting of top frame TF and the manner of locating the axes of added rolls RB3 and RTZ will be explained in connection with FIG. 5. For the present, it is sufficient to note that the axis for RTZ is a bit lower than the horizontal plane containing the axis of RT1 and the offset as measured in a horizontal plane is reduced by about five percent. Thus as an example, using 1 /2" rolls, RBI and RB2 are offset 2 diameters (3" in this example) whereas RT1 and RT2 are offset 2%". RT2 has its axis offset downwardly from the axis of RT1 (a horizontal plane containing the axis of RT1 is offset downwardly from a horizontal plane containing RT2) by about .03". This offset is not critical and the amount is due in part to desired straightening characteristics. As top rolls are added, and with the pivot axis below the bottom rolls and beyond the last roll, the added top roll axes are successively dropped by about the same amounts.

Added bottom roll RB3 has its axis in the horizontal plane containing the axes of bottom rolls RBI and RB2. Preferably, though not necessarily, the triangle formed by the centers of rolls RB2; RB3 and RT2 is isosceles; the two equal sides extending downwardly from the center of RT2. In that case RB2 has its axis laterally offset from the RB2 axis by a bit less than 2 diameters, in this example by 3 inches less about A".

In the example given, PA is .5625" below the line of centers of the bottom rolls and the horizontal offset of each bottom roll is as follows: RBI, 9 inches; RB2, 6 inches; RB3, 3% inches.

Similarly, the top roll offset is RT1, 7 /2 inches; RT2, 4% inches.

A graphical procedure for locating the axes of straightener rolls utilizing the invention will now be dis closed in connection with FIG. 5. Pivot axis PA has horizontal fulcrum base line FBL drawn from PA. Line FBL here happens to lie below the bottom roll line of centers BLC, but can well be even with it or above it. Arc K1 with PA as a center is drawn so that point VI on line of centers for bottom rolls BLC is located as the position of bottom roll BR1. In fact, point VI can be arbitrarily selected on line BLC, the location of such point depending upon the number and size of rolls. Point V2 on line BLC is selected to be spaced from VI two roll diameters. Point /2 on line BLC midway bet-ween points VI and V2 locates vertical bisector VVz and point T1 is selected at an elevation above BLC which is substantially equal to one roll diameter plus maximum stock thickness. Are K2 from PA as a center to point T1 as radius describes the locus of the axis of TR1 when the top frame pivots about PA.

The next point T2 defining the second top roll is obtained as follows. A point is initially assumed on a level with T1 and vertically above an assumed point /2A which is beyond V2 the same distance as V2 is beyond /2 In short, initially V2 is equidistant between /2 and /2A. Arc K4 is drawn from PA to assumed point T2. It will be noted that the slope of arc K4 near assumed point T2 is quite steep. It will be found that assumed point T2 can be moved along arc K4 where T2 will be somewhat lower than T1 and will be ofiset horizontally from V2 somewhat less than the offset of T1 from V1 in a horizontal direction. Dropping a vertical line from now fixed point T2 will accurately locate /2A on line BLC. Point V3 locating the axis of the third bottom roll is accomplished by having /2A midway between V2 and V3. Point T2 is located above line BLC approximately the same distance as point T1, depending upon the location of fulcrum axis PA and desired straightener characteristics. Some variation of point T2 obviously can be tolerated.

As rolls are added, the same procedure is followed, except that /2A and T2 will be the reference points. Thus an added T3 will end up a bit lower than T2.

Referring now to FIGS. 6, 7 and 8, an embodiment of a straightener utilizing the invention is illustrated. Base plate 10 is a fiat, rectangular plate of steel, heavy enough to support various parts. In practice plate 10 may have a thickness of the order of about /2 or /1 inch, depending upon how many rolls are to be provided and the length of rolls. Plate .10 may have a length of about 12 or 15 inches for most sizes and a width of from about 6 inches and up, depending upon the width of stock to be handled. As a rule, the width of plate 10 must be great enough to accommodate the length of rolls used; and the roll length must be somewhat greater than stock width. Rigidly secured to plate 10 along the sides are side plates 12 and 13 in which are journalled bottom rolls 15, 16 and 17.

Each roll may have a small diameter, as for example from about 1 to 1 /2 inches, although it is to be understood that this is simply an example of how the new straightener can utilize small diameter rolls without limiting its stock handling range. The rolls may be chrome plated and polished and the roll construction can be substantially lighter than any conventional comparable straightener. The manner of mounting each roll in bearings supported in sides 12 and 13 is conventional. Sides 12 and 13 are of thick steel such as about depending upon the expected loading during operation. As previously set forth, the axes of bottom rolls 15, 16 and 17 are in a horizontal plane in the normal operating position of the straightener. The rollsare supported high enough to clear the top face of base plate 10 and their relative spacing follows the principles previously set forth.

It is understood that roll 15 is nearest the front or intake end of the straightener. Toward the rear end of the straightener, pivot means 20 and 21 are rotatively supported in sides 12 and 13. Pivot means 20 and 21 are carried in support plates 22 and 23 rigidly secured to top frame side plates 24 and 25. Cross plate 27 is attached to top side plates 24 and 25 and serves to cover the top frame 26 and strengthen the frame. As will be described in detail later, the top frame is further reenforced by added steel parts inear the fronth end of the straightener. Top frame 26 carries top rolls 26A and 26B journalled for rotation with their axes located as set forth in connection with FIG. 5. The entire top frame can swing about pivot means 20 and 21 and the down position of the top frame on the bottom frame is adjustable by stop pins 30. These stop pins are threadedly secured in the top frame on opposite sides of the frame and cooperate with recesses in the bottom frame to limit the closing position of the top frame.

Any other limiting means may be provided. Preferably the straightener is provided with spring means tending to open the top frame and rigid locking means to hold down the top frame to the lowest position determined by the stop pin means. Accordingly, compression springs 32 are set into the lower frame sides and cooperate with recesses in the top frame. These springs are stiff enough so that the top frame is strongly biased to an open position. The locking means provides a powerful force to close the top frame to the lowest positionas determined by adjusting stop pins 30.

Supported on base plate 10 forwardly of side plates 12 and 13 is support structure 35 consisting of side plates 36 and 37 and top cross plate 38. Rotatively secured in cross plate 38 is post 40 extending upwardly and carrying cross pin 41 at the upper end of post 40. Clevis 42 has its arms straddling post 40 with cross pin 41 functioning as the clevis pin. Clevis 42 carries handle 43. Clevis 42 has its side edges 44 shaped as cam surfaces so that handle 43 when extending upwardly as in FIG. 7 will clear the top of locking bar 48. When clevis handle 43 is down, as in FIG. 6, cam edge 44 presses locking bar 48 down.

Locking bar 48 has elongated slot 49 through which pin 40 passes and, in the unlocked position of clevis 42 (handle '43 up) permits locking bar 48 to be moved longitudinally. In the positions hown in FIG. 6, locking bar 48 has end portion 48a overhanging and bearing down on top of pillow block 27A of the forward end of the pivotted frame supporting the top rollers. Forward end 48b is slotted and clears an adjustable stop screw arrangement 50 to cooperate with locking bar 48 so that end 48b may have to stop to press against when locking bar 48 is urged down during the cam lock action. Spring 51 about pin 40 normally has locking bar 48 upwardly when handle 43 is in unlocking position.

Side plates 37 support auxiliary plates 53 in which are journalled threshold rolls or rods 55 for initially guid ing stock at proper height into the straightener. Stock edge guides 53A, adjustable along rods 55, are provided. It is understood that suitable pull-through means beyond the discharge or exit end of the straightener will be provided. Such means are in wide use with straighteners and function to grip stock and pull the same through a straightener. It is possible to add power driven rolls to a straightener and make a unitary structure.

A straightener embodying the present invention compared to a conventional straightener for handling the same stock will weigh about /2, cost from about 20% to 50% less than the conventional straightener and require about 50% of pull on stock to straighten the same. Apart from the above advantages, the new straightener can be opened easier for cleaning or loading and may be more easily set for desired stock thickness.

The lowering of the axes with respect to the axis of the front top roll provides for maintenance of adequate separation between the top and bottom roll axes when the top rolls are in the closed position and the top frame has been adjusted to handle a thick stock. This is due to the geometry of the system incident to the pivotal mounting of the top frame. The straightener will function satisfactorily even if the downward offset of the top roll axes is omitted.

What is claimed is:

1. In a pull-through straightener for metal strip stock having a Width up to the order of about 40" and a thickness up to the order of .100", said Straightener having a bottom series of cylindrical rolls disposed so their axes are parallel, laterally offset and normally lying in a generally horizontal plane for normal operation, said rolls having equal diameters, at least the first two bottom rolls having their respective axes spaced from each other substantially two roll diameters, said straightener also having a top roll series, said top and bottom rolls having substantially equal diameters, said top rolls having their respective axes laterally offset and parallel, all top and bottom rolls being parallel, each top roll having its axis so that the projection thereof on the lower horizontal plane containing the lower roll axes lies between two adjacent lower roll axes, said top rolls being disposed substantially one roll diameter above the aforementioned lower horizontal plane, said straightener having at least two top rolls and three bottom rolls for straightening purposes, means for mounting said bottomrolls in a bottom frame in fixed axial positions, a top frame, means for mounting said top rolls in fixed axial positions in said top frame, and means for rigidly securing said top and bottom frames in fixed relative position for straightener operation, all said straightener rolls being free running, said straightener being characterized by relatively light roll and bearing construction, low pull-through power requirements, fixed relative top roller orientation for various stock thicknesses, and a generally lighter construction in comparison to a conventional straightener for handling similar stock.

2. The construction according to claim 1 wherein means are provided for determining the relative vertical position between the top and bottom frames for adjusting the vertical spacing between top and bottom rolls.

3. The construction according to claim 2 wherein readily releasable means are provided for rigidly locking said top frame to said bottom frame in predetermined adjusted position.

4. The construction according to claim 1 wherein means are provided for pivotally securing said top frame to said bottom frame, said pivot axis being located so that it is parallel to the roll axes and is located near an end of the straightener.

'5. The construction according to claim 4 wherein said pivot axis is located near the exit end of the straightener.

6. The construction according to claim 5 wherein in the operating position, the second top roll axis beginning from the inlet end of the straightener is vertically offset somewhat from the axis of the first top roll.

7. The construction according to claim 1 wherein added rolls beyond the first top roll and beyond the first two bottom rolls are provided, the spacing between adjacent rolls in the top series and the spacing between adjacent rolls in the bottom series being somewhat less than the spacing between the first two bottom rolls.

8. A pull-through straightener for metal strip stock having a bottom array of cylindrical rolls disposed so their axes are parallel, laterally offset and normally in a generally horizontal plane for operation, said rolls halving equal diameters and being rotatively supported in a frame, at least the first two bottom rolls from the intake end having their respective axes spaced from each other substantially two diameters, said straightener also having a top roll array rotatively supported in a top frame, said top and bottom rolls having substantially equal diameters, said top rolls having their respective axes laterally offset and parallel, there being at least two top rolls, ali top and bottom rolls being parallel, each top roll having its axis so that the projection thereof on the lower horizontal plane containing the lower rolls lies between two adjacent lower roll axes, said top rolls being disposed substantially one roll diameter above the aforementioned lower horizontal plane during stock straightening, said straightener having at least two top rolls and three bottom rolls for straightening purposes, means for pivotally mounting said top frame about a pivot axis parallel to and laterally offset from the roll axes, said pivot axis being below the roll axes and beyond the outlet end rolls of the straightener away from the inlet end, adjustable means for limiting the closing travel of the top frame on the bottom frame to adapt the straightener to stock thickness, spring means biasing the top frame against full closure, and manual means adjacent the inlet end of the straightener for forcing the top frame against the lower frame to the position determined by the adjustable closure limiting means to maintain the straightener in operarive-position during straightening action.

9. The construction according to claim 8 wherein said last nalmed manual means includes a bar slidably supported on a stationary support forwardly of the top frame near the intake end of the straightener, said bar being movable to a top frame locking position overlying the top frame end and movable to an unlocking position where it clears the top frame, and oam means operated by a handle for forcing the top frame into locking position.

References Cited UNITED STATES PATENTS MILTON S. MEHR, Primary Examiner 

